follow up on or to

[thomas615]

I am not sure "on" or "to" after follow up. Which sentence is correct? My answer is (1). Correct?


1)We are writing to follow up on our letter of January 25th.



2)We are writing to follow up to our letter of January 25th.

 

[billmcd]

I am not sure "on" or "to" after follow up. Which sentence is correct? My answer is (1). Correct? Yes, but you could write as, "We are writing as a follow-up to our letter of January 25th".


1)We are writing to follow up on our letter of January 25th.



2)We are writing to follow up to our letter of January 25th.

b.